2 Answers
2

Well obviously to produce a lot of bass you're going to need a big driver. All I can suggest is trying to track down a second hand sub or bass guitar amp and running ultra-low frequency test tones through them at high levels.

Do you have access to the amp or monitors that will be used in the room you are soundproofing? If so, generate a sine wave sweep in Audacity that goes from 20 Hz to 200 Hz. Loop it. Then crank the volume as high as you can.